Glass

Amethyst druzy cluster

Amethyst, purple quartz (SiO₂)

Amethyst-bearing quartz

Quartz, SiO₂; purple coloration from trace iron and irradiation

Pink quartz (likely rose quartz)

Quartz, silicon dioxide (SiO₂), typically massive rose quartz colored by trace elements and microscopic inclusions

Smoky Quartz (Vein Quartz)

Quartz (Silicon Dioxide, SiO2)

Obsidian

Volcanic glass (SiO2 - Silicon Dioxide)

Sea Glass

Amorphous silicon dioxide

Amethyst (Rose-tinted variation)

Silicon Dioxide (SiO2) with trace iron impurities

Quartz (Clear Quartz/Rock Crystal)

Silicon Dioxide (SiO2)

Quartz (Milky/Smoky variety on matrix)

Silicon Dioxide (SiO2)

White quartz bead bracelet (likely milky quartz)

Quartz, silicon dioxide (SiO₂), usually microcrystalline or cloudy crystalline quartz

Milky quartz (likely quartz-rich fragment)

Quartz, silicon dioxide (SiO₂)

Milky Quartz

Silicon Dioxide (SiO2)

Pumice

Pumice (Vesicular Felsic Igneous Rock)

Chert / Flint

Microcrystalline or Cryptocrystalline Quartz (SiO2)

Milky quartz fragment (likely quartz-rich mineral)

Quartz, silicon dioxide (SiO₂)

Clear quartz tumbled stone

Quartz (silicon dioxide, SiO₂)

Milky quartz (likely)

Quartz, silicon dioxide (SiO₂)

Mixed river-worn rock and mineral collection

Mostly quartz/quartzite, feldspar-bearing granitoid, chert, and mafic volcanic rocks; exact species vary by pebble

Clear quartz crystal (likely quartz fragment)

Quartz, silicon dioxide (SiO₂)

Muscovite (Mica) in Quartz Matrix

Muscovite (KAl2(AlSi3O10)(OH)2) and Quartz (SiO2)

Snowflake Obsidian

Spherulitic Volcanic Glass (primarily SiO2 with Cristobalite inclusions)

Chert (Flint)

Silicon Dioxide (SiO2)

Chert (Flint variety)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Clear Quartz Moon Pendant

Silicon Dioxide (SiO2)

Jasper Shard / Chert

Silicon dioxide (SiO2)

Chert / Chalcedony

Silicon Dioxide (SiO2)

Chert (specifically Flint or Common Chert)

Silicon dioxide (SiO2) - Microcrystalline quartz

Flint or Chert

Microcrystalline Quartz (SiO2)

Sea Glass / Beach Agate Pebble

Silicon Dioxide (SiO2)

Green faceted or cabochon gemstone (possibly glass or synthetic)

Undetermined; possibilities include green beryl (Be₃Al₂Si₆O₁₈), quartz (SiO₂), or synthetic glass

Blue glassy gemstone-like specimen

Indeterminate; possibly dyed or treated turquoise, blue apatite, or man-made glass

Quartz (Smoky/Clear variety)

Silicon Dioxide (SiO2)

Quartz (Crystal Fragment)

Silicon Dioxide (SiO2)

Quartz (specifically Clear Quartz or Rock Crystal)

Silicon Dioxide (SiO2)

Polished mahogany obsidian

Volcanic glass; predominantly rhyolitic silica glass (SiO₂-rich)

Green obsidian (likely moldavite)

Natural volcanic glass; if extraterrestrial-impact glass, moldavite (tektite)

Black obsidian

Volcanic glass (mostly rhyolitic silica glass; SiO₂-rich)

Tumbled black obsidian (likely)

Volcanic glass; chiefly silica-rich rhyolitic glass (SiO₂)

Obsidian (likely snowflake or smoky obsidian fragment)

Volcanic glass; predominantly rhyolitic silica glass (SiO₂-rich)

Blue Goldstone

Synthetic Aventurescent Glass (Cobalt-doped soda-lime glass)

Blue Goldstone

Aventurine glass (Synthetic borosilicate glass with cobalt and metallic inclusions)

Sea Glass

Amorphous silicon dioxide (Man-made glass weathered by wave action)